1. Field of the Invention
The invention relates to apparatus for and methods of drilling holes through generally inaccessible structural members concealed within hollow walls and pulling flexible lines through those holes.
2. Background Information
Flexible lines, such as electrical power wires or cables, telephone wires, coaxial video entertainment cables, fiber optic signal transmission lines, water lines (e.g., for a refrigerator's ice maker), etc., can be relatively easily positioned within the walls of a building or above a ceiling of the building if those lines are installed after framing, but before the walls or ceilings are completed. This approach is customary for new construction. Once the structure has been completed, however, adding, replacing, or moving lines within a hollow wall, in a restricted crawl space above a ceiling or beneath a floor is a much more difficult task.
In many remodeling or "old work" situations in single story residences a new line of some sort or another (e.g., a three conductor non-metallic sheathed electrical power cable) is run through an attic crawl space and down through a hollow wall to a service point (such as a point where an electrical outlet box is to be installed a foot or so above a floor, or a switch box located several feet above the floor). Ideally, to avoid damaging and replacing large portions of the wall surface, a job of this sort requires cutting or drilling a hole through the top plate of the wall, shoving the line through that hole and feeding it to a small access hole cut into the hollow wall. The necessary hole can be drilled from the attic and the line shoved down through the top plate only if there is adequate working clearance--e.g., if the vertical distance between the top plate and closest roof truss, roofing panel or other obstacle above it is great enough that a workman can put an electric hand drill into position to drill through the top plate. If the service point is located on an exterior wall, this approach commonly fails completely because the vertical free space between the top plate and the lowest overhead roof member is too small. Moreover, even when there is working clearance, there is always a chance for the worker to drill the hole through the top plate between two adjacent wall studs and then find that access hole had been cut between two other walls studs. This commonly requires a second trip into the attic crawl space to drill another hole.
It is known in the prior art to use a drill having a flexible shaft to drill the hole from below, then securing access to the hole from above and feeding the line through the hole. Again, working on an exterior wall can pose an insurmountable problem if there is so little clearance between the upper surface of the top plate and an overhead roof member that a worker can not reach the hole in order to feed the line through it. It is thus desirable to have a means whereby a worker can insert a tool through a small access hole in a hollow wall, drill a hole in a top plate of that wall, and fish a line through the drilled hole even if there is very little vertical clearance between the top plate and a roof member disposed above it. It will be understood to those skilled in the art that similar situations occur when cutting through a sill into a lower floor or a crawl space beneath a house.
A number of US patents are notable among prior art references in this area. These include:
U.S. Pat. No. 1,408,802, wherein Crocker et al. teach a flexible drill shaft turning within a flexible coaxial guide tube for use in drilling holes through a plurality of ceiling joists. Crocker et al. provide a collapsible and expandable guide device mounted behind the drill head. Their guide device is adapted to collapse when pushed through a hole in a joist, and to expand under the influence of bias springs when free of the joists. When in its expanded configuration, the guide device acts to space the drill bit away from the upper surface of a ceiling by some preset amount, thus ensuring that each of a plurality of holes is made at the same distance above the ceiling. PA1 U.S. Pat. No. 2,958,349, wherein McNutt teaches the use of a drill bit rotated by a flexible shaft encased in a rigid guide tube. The drill bit is translated toward the work through a bushing affixed adjacent one end of the guide tube. PA1 U.S. Pat. Nos. 3,611,549 and 3,697,188, wherein Pope discloses a flexible-shafted drilling apparatus for forming holes in and installing lines through structural members concealed within hollow walls. Pope teaches the use of a drill bit having a throughhole transverse to the axis. A line or a line leader of some sort can be fed through the throughhole to attach the line to the drill bit, which is then pulled back towards the drill operator by means of the flexible shaft. Pope also teaches the use of a separate tool for guiding his drill bit into cutting contact with the concealed structural member. PA1 U.S. Pat. No. 5,395,188, wherein Bailey et al. teach the use of a curved, rigid guide for positioning a drill bit attached to flexible shaft so as to drill an upwardly angled hole from a starting point near a floor to a finishing point within a hollow wall. Bailey et al. teach the use of their drill guide to drill through the wall and the wall sill or sole plate.